1. Field of the Invention
The present invention relates to a high frequency magnetic material suitable for constituting a nonreciprocal circuit device for high frequencies, for example, a circulator and an isolator, and to a high-frequency circuit component configured using the magnetic material for high frequencies.
2. Description of the Related Art
By adopting a laminated structure in ceramic electronic components, such as monolithic capacitors and laminated inductors, electronic components can be miniaturized. As a result of miniaturizing the electronic components, electronic equipment configured using the electronic components can also be miniaturized.
The laminated ceramic electronic components are manufactured, generally, by the steps of preparing a plurality of ceramic green sheets, forming internal conductors on specified ceramic green sheets by screen printing, vapor deposition, etc., laminating these ceramic green sheets, and baking the resulting green laminate.
In the laminated ceramic electronic components produced by the aforementioned manufacturing method, the ceramic material must sinter at a temperature equivalent to, or lower than, the melting points of the used internal conductor materials since the ceramic material is baked at the same time with the internal conductors.
In the area of communication equipment, radio communication apparatuses have been miniaturized in recent years, and available frequency bandwidth has been increased. Therefore, requirements for miniaturization, increase in bandwidth, cost reduction, etc., of circuit components used in this area have intensified.
As typical high-frequency circuit components used in the aforementioned area of the communication equipment, for example, high-frequency nonreciprocal circuit devices, such as circulators and isolators, are mentioned. The aforementioned nonreciprocal circuit device is primarily composed of a plurality of central conductors insulated from each other and arranged to intersect with each other, a magnetic material for high frequencies arranged intimately contacting with the central conductors, and a permanent magnet applying a direct current magnetic field to the central conductors and the magnetic material for high frequencies. Each of these constituents is produced as an independent component, and is subjected to use in combination with other components.
In order to meet the aforementioned requirements for miniaturization, increase in bandwidth, cost reduction, etc. of the aforementioned high-frequency nonreciprocal circuit devices, it has been suggested to produce the magnetic material for high frequencies and the central conductors by integral sintering instead of producing each of the components independently, as described in, for example, Japanese Unexamined Patent Application Publication No. 6-61708. In this publication, also described is the use of palladium or platinum as the material for the central conductor.
In the high-frequency nonreciprocal circuit devices produced by the aforementioned integral sintering, for example, a Caxe2x80x94V-based garnet material is used as the magnetic material for high frequencies. This Caxe2x80x94V-based garnet material must be baked at a temperature of 1,300xc2x0 C. or more in order to produce a dense sintered material. When the temperature is lower than this, sufficient sintering density cannot be achieved and this causes problems in that the ferromagnetic resonance half width becomes large and many pores are present.
Palladium or platinum has the advantages of a high melting point of 1,300xc2x0 C. or more, and ease of integral sintering with the magnetic material for high frequencies made of Caxe2x80x94V-based garnet material. However, it has a disadvantage of high resistivity, so that, for example, the insertion loss becomes large in the use for a laminated isolator device.
In order to solve the aforementioned problem, it has also been suggested in, for example, Japanese Unexamined Patent Application Publication No. 7-212108 that the central conductor be composed of, or primarily composed of, silver and the central conductor be integrally sintered with the magnetic material for high frequencies.
However, since silver has a low melting point of 961xc2x0 C., the magnetic material for high frequencies must be sintered at a low temperature equivalent to, or less than, the melting point of silver or the conductor primarily composed of silver. When the magnetic material for high frequencies is not sufficiently sintered, a material having a small loss cannot be produced due to its low density.
In order to achieve sufficient sinterability in concurrent baking with silver or the conductor primarily composed of silver, for example, a Bixe2x80x94Caxe2x80x94V-based garnet material in which Bi is added to a Caxe2x80x94V-based garnet material, may be used as a magnetic material for high frequencies which can be sintered at a low temperature of 1,000xc2x0 C. or less, and low softening point glass may be added to a magnetic material for high frequencies, although in these cases, a magnetic material for high frequencies having a small loss cannot be produced due to generation of different phases, etc.
Accordingly, it is an object of the present invention to provide a magnetic material for high frequencies and a high-frequency circuit component configured using this magnetic material for high frequencies, which can solve the aforementioned problems.
In order to solve the aforementioned technical problems, according to an aspect of the present invention, a magnetic material for high frequencies primarily composed of yttrium iron-based garnet, in which calcium (Ca) substitutes for a part of yttrium (Y) site, and vanadium substitutes for a part of iron (Fe) site, is provided, wherein 0% to about 0.5% by weight of oxide of tetravalent or pentavalent element, other than V, is present, and the ratio of Ca atoms to V atoms, Ca/V, falls within the range of 2.0 less than Ca/Vxe2x89xa62.4.
In the magnetic material for high frequencies according to the present invention, at least one of bismuth (Bi) and gadolinium (Gd) may substitute for a part of Y site, at least one of aluminum (Al) and indium (In) may substitute for a part of Fe site, or the aforementioned substitutions of both sites may be performed.
The magnetic material for high frequencies according to the present invention is preferably produced by baking at a temperature of 1,100xc2x0 C. or less.
According to another aspect of the present invention, a high-frequency circuit component configured using the aforementioned magnetic material for high frequencies is provided.
The high-frequency circuit component is provided with a plurality of central conductors insulated from each other and arranged to intersect with each other and a magnetic material for high frequencies arranged intimately contacting with the central conductors. This magnetic material for high frequencies is composed of the aforementioned magnetic material for high frequencies according to the present invention. The central conductors and the magnetic material for high frequencies are integrally sintered, and a direct current magnetic field is applied to the central conductors and the magnetic material for high frequencies by a permanent magnet.
The high-frequency circuit component according to the present invention is preferably a high-frequency nonreciprocal circuit device.